Direct injection engines are engines wherein fuel injection occurs inside the engine's cylinders. The fact that the fuel is injected directly into the cylinders enables precise control over the amount of fuel burned and the timing of injection. However, a problem with these engines is that intake valve deposits tend to build up to unacceptable levels. These deposits interfere with valve closing, valve motion and valve sealing. They reduce the efficiency of the engine and limit maximum power. The present invention provides a solution to this problem.